2Gig at 800 or 3Gig at 667?

I just bought a new imac (2.8GHz). Should I leave in the 2 gig of RAM at 800 MHz that came with it, or put in a 3 gig at 667 (1gig + 2gig stick) set that I have extra just laying around?

I'm thinking that it would be stupid to mix one of the faster 1gig sticks with the slower 2gig (1gig @800 + 2gig @667) because I believe that limits the faster one to 667 anyways.

So, 3 running slower or 2 running faster, which is the better deal?

I am not a photo/video guy. I am an engineering student. I will be using the computer for school and personal tasks (music, internet browsing, word processing, programming, simulation software) and doing virtualization with vmware.

I am thinking that the capacity of the 3 gigs is more advantageous than the speed of the 2 gigs because I wont notice/care about a couple seconds and I tend to leave firefox with lots of tabs open and extensions running open most of the time as well as many other applications. I am not an expert though and possibly you know something I don't about these matters, so help me out!

Never mix different types of ram, much less the speed. Try to have it in parallel, like 2 x 2GB ram of the same manufacturer or 2 x 1GB ram. Don't mix. The speed differences won't affect you that much, you probably won't even notice the change.

As for firefox with tabs, I used firefox with 5-10 tabs open with 512MB ram on an iBook G4. Long since gone, but 2GB is plentiful for your needs. If you want, upgrade to 4GBs of ram, for around 70-80 dollars. Make sure its the same brand, same speed, and same amount in each ram slot. Dual cores benefit if you use the same amount of ram in each slot, one slot for each core. Having different speeds and different amounts can affect the performance. That's why its recommended to do it in parallel.

I'm just quoting what the apple support pages show. Mixing sizes doesn't affect system performance for the single core infrastructures, but for the newer intel dual cores, parallel ram is important for optimal performance, as quoted by Intel, AMD, and Apple. Just my 2 cents.

I realize that mixing speeds doesn't make for any benefit. I also would not be mixing brands, the 1 and 2 gig stick that I would replace with are same speed, manufacturer, and timings (I assume this last one because they originally came out of the same laptop, Dell w/ core2 duo).

I am also aware of the threading benefits that having identical memory offers. I have heard that it isn't that significant though having 150% of the memory is better.

Here are some tests involving matched/non matched pairs of RAM, done with macbook, but you get the point

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Thank you. That information was very useful. It appears that 3Gig preforms better than 2Gig in almost all settings. I bet that they are using the same speed RAM in the test whereas I have the complication that my 3Gig set runs at a lower clock speed, but I think that I will try out it out regardless. Thanks.

3GiB performs better than 2GiB only when 2 GiB is not more than enough. There's a lot of naive users that think that adding more memory always makes a computer faster.

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I literally have the 3Gigs just sitting around. They are extra and I dont have any other systems that take DDR2 SODIMMs. I am wondering if it is wise to go ahead and use them or to just continue to admire them on my desk.

I don't know what the CAS level means. If it refers to timings, I still can't answer because both sets are manufacturer parts that came with the machines and I don't know how to determine that information without any documentation from the cards.

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